Flowmeter with element for reducing the formation of turbulence in the flowing medium

ABSTRACT

Devices for determining at least one parameter of a flowing medium having an inner pipe according to the related art have the disadvantage that whirls are formed, which causes increased signal noise at the measuring element and pressure drop. A device ( 1 ) is described which has an element ( 11 ) that reduces the whirl formation in the flowing medium.

BACKGROUND INFORMATION

The present invention is based on a device for determining at least oneparameter of a medium flowing in a duct according to the preamble ofclaim 1.

German Patent Application 197 35 664 A1 describes a device in which aplug sensor having a measuring element is situated within a pipe throughwhich the medium flows, an upstream end of the pipe extending to afilter chamber. However, whirls are formed in the area of theincident-flow edge of the inner pipe, resulting in increased signalnoise at the measuring element.

German Patent Application 196 52 753 A1 describes a device having ameasuring element, which contains a flow straightener for straighteningthe flow and a screen for stabilizing a measuring signal. However, noinner pipe is used in this device to protect the measuring elementagainst the effect of dirt particles or water droplets.

SUMMARY OF THE INVENTION

The device according to the present invention having the characterizingfeatures of claim 1 has the advantage compared to the related art thatthe pressure drop and signal noise are reduced in a simple manner.

Advantageous refinements of and improvements on the device named inclaim 1 are made possible by the measures given in the dependent claims.

It is advantageous to situate a incident-flow edge of a barrel ring atapproximately the same axial length as an external incident-flow edge ofthe inner pipe, since the barrel ring must only be extended in the axialdirection.

DRAWING

An exemplary embodiment of the present invention is schematicallyillustrated in the drawing and explained in detail in the descriptionthat follows.

FIG. 1 shows an exemplary embodiment of a device designed according tothe present invention;

FIG. 2 shows an axial cross-section of FIG. 1.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

FIG. 1 shows a device 1 designed according to the present invention infront view. Device 1 includes a duct 5, into which a plug sensor 3 maybe inserted, for example. A medium flows in duct 5 in the flow direction7. i.e., in a direction which is perpendicular to the plane of thedrawing. A flow straightener 9, secured in duct 5, is situated upstreamfrom plug sensor 3, for example. A barrel ring 13, for example, a shortpipe element, used to secure an inner pipe 17, is connected to flowstraightener 9, for example. Barrel ring 13 has at least one brace 15,which connects barrel ring 13 to inner pipe 17 or a diverting screen 19,securing inner pipe 17 in flow straightener 9 or in duct 5. Inletopening 21 area of inner pipe 17 has diverting screen 19, for example.Diverting screen 19 is used to reduce the effect of foreign particlessuch as liquid or solid particles, for example, on measuring element 33situated downstream (FIG. 2). The design of such a measuring element 33is sufficiently known to those skilled in the art, for example, fromGerman Patent Application 195 24 634 A1, whose disclosure is an integralpart of the present Patent Application.

FIG. 2 shows an axial cross section of device 1 of FIG. 1.

Inner pipe 17 has a central axis 18. The top of FIG. 2 (part of innerpipe 17 between central axis 18 and plug sensor 3) shows the related artwithout element 11 and the bottom of FIG. 2 shows the embodimentaccording to the present invention having element 11.

At the periphery of its end face 23, inner pipe 17 forms an outerincident-flow edge 25, around which the medium flows. Barrel ring 13 hasan inner incident-flow edge 27.

In this embodiment, flow straightener 9 is situated downstream frominlet opening 21. Therefore, in the area of incident-flow edge 25,whirls 29 are formed according to the related art, as a flow line 31indicates in FIG. 2. This results in increased signal noise at measuringelement 33 and a higher pressure drop in duct 5 and inner pipe 17.

An element 11 is situated in the proximity of the outer incident-flowedge 25 of inner pipe 17, for example, on inner pipe 17, and reduces thewhirl formation in the flowing medium. This may take place, for example,by applying an additional streamline-shaped elevation on inner pipe 17,which accelerates the flowing medium.

If incident-flow edge 27 of barrel ring 13 is approximately at the sameaxial height as outer incident-flow edge 25 of inner pipe 17, thesewhirls 29 are also no longer formed, since the area of passage for theflow in duct 5 is reduced at approximately the axial height of inletopening 21 and the flowing medium is accelerated, whereby the whirlformation or the number of whirls formed is reduced. Depending on theflow conditions, whirls rotating in the opposite direction may also beformed, compensating the other, interfering, whirls according to therelated art. With this design of barrel ring 13, element 11 is formed inorder to reduce the whirl formation.

Thus, the flow in and around inner pipe 17 is stabilized, and the signalnoise at measuring element 33 and the pressure drop are reduced.

Measuring element 33, which determines at least one parameter of aflowing medium, is situated within plug sensor 3. Parameters of aflowing medium include the air volume flow rate for determining an airmass, a temperature, a pressure, a concentration of a medium component,or a flow velocity, which are determined using appropriate sensors.Device 1 can be used for determining further parameters. This can beaccomplished by using two or more sensors, one sensor being capable ofdetermining two or more parameters.

1. A device for determining at least one parameter of a medium flowingin a duct, comprising: an inner pipe at least partially situated in theduct, the inner pipe having an inlet opening; at least one plug sensorin the inner pipe, the at least one plug sensor containing at least onemeasuring element for determining the at least one parameter of theflowing medium; an element for reducing a whirl formation in the flowingmedium, the element being situated in an area of the inlet opening ofthe inner pipe; and a barrel ring at least partially securing the innerpipe in the duct, the barrel ring having an inner incident-flow edgeabout at the same axial length as an outer incident-flow edge of theinner pipe, forming the element for reducing the whirl formation.
 2. Thedevice according to claim 1, wherein the duct has a flow straightener atabout the same axial length of the inlet opening.
 3. The deviceaccording to claim 2, wherein the barrel ring is coupled to the flowstraightener.
 4. The device according to claim 1, wherein the inner pipehas a diverting screen in an area of the inlet opening.
 5. The deviceaccording to claim 1, wherein the at least one parameter includes avolume flow rate.
 6. The device according to claim 1, wherein the mediumflowing in internal combustion engine.